1. Technical Field
The present invention relates to a piezoelectric unit to be displaced upon applying a voltage to a piezoelectric element, and a liquid ejecting head and a liquid ejecting apparatus that include the piezoelectric unit.
2. Related Art
A liquid ejecting head has thus far been known that includes a vibration plate constituting a part of a pressure chamber communicating with a nozzle opening through which ink droplets, an example of the liquid, are dispensed, in which the vibration plate is deformed by a piezoelectric element so as to pressurize the ink in the pressure chamber to thereby dispense the ink droplets through the nozzle opening. As well, a liquid ejecting apparatus including such a liquid ejecting head is also known. Some ink jet recording heads, exemplifying the liquid ejecting head, employ a vertical vibration type piezoelectric unit that expands and contracts in an axial direction of the piezoelectric element. The vertical vibration type piezoelectric unit thus far developed include the one having a piezoelectric element block that includes a plurality of multilayer piezoelectric elements each including a common internal electrode, an individual internal electrode, and a piezoelectric material layer interposed therebetween, the piezoelectric element block being connected to a fixing substrate, for example as disclosed in JP-A-2004-327462.
The piezoelectric element block includes a distal end portion which is a free end, and a base end portion connected to the fixing substrate, and a driver wiring is connected to the base end portion. The common external electrode connected to the common internal electrode and the individual external electrode connected to the individual internal electrode are formed so as to reach the base end portion, and the driver wiring is connected to the common external electrode and the individual external electrode at the base end portion.
Normally, a silver/palladium alloy is employed as the material of the common internal electrode and the individual internal electrode, because of the sintering shrinkage that agrees with that of the piezoelectric material layer, close adhesion therewith, and high reliability (see, for example, JP-A-2011-56731 and JP-A-2011-71365).
However, the palladium, which is a rare metal, contained in the silver/palladium alloy constituting the common internal electrode and the individual internal electrode inevitably raises the manufacturing cost. Although a part of the common internal electrode or individual internal electrode located in an inactive region which is not involved in the vibration performance may be excluded for the purpose of cost reduction, in which case, however, the thickness of the base end portion in the inactive region where those electrodes are layered is changed, and therefore the connection with the driver wiring and positioning therewith by connection to the fixing substrate become difficult.
Therefore, it has been difficult to reduce the manufacturing cost of the piezoelectric unit, the liquid ejecting head, and the liquid ejecting apparatus while keeping the thickness of the base end portion of the piezoelectric element block unchanged.